feat(connections): Add alias field to invitation response schema

[MonolithicMonk]

This PR adds the alias field to the invitation response schema

Changes:

• Extended InvitationResultSchema to include an optional alias field.
• Added descriptions and examples for the alias field in the OpenAPI documentation.

Why:

• This change allows tools like openapi-generator to generate the correct interfaces / classes for the /connections/{conn_id}/invitation endpoint

Testing:

• Verified that the alias field is included in the response when fetching an invitation.
• Confirmed that the OpenAPI documentation reflects the new field.